Charles Sturt University
Graham Centre for Agricultural Innovation

Increasing winter crop production in southern Australia by improving the capture, storage and use of summer fallow rain

Increasing winter crop production in southern Australia by improving the capture, storage and use of summer fallow rain

Date :  Thursday, 14 October 2010
Time :  3.00pm
Venue : Conference Room, Wagga Wagga Agricultural Institute
Presenter : James Hunt, CSIRO Plant Industries, Canberra

Abstract

In regions of Australia dominated by winter rainfall, rain that falls during the summer fallow period has not traditionally been valued as a resource for production. Recent years of below-average growing season rainfall has forced a revaluation of this notion, and significant research is being invested in management practices which seek to maximise capture and use of summer fallow rain.

This presentation describes a) a modelling approach which quantifies the potential value of summer fallow rain as a resource to winter crop production across southern and western Australia, and b) results from ongoing field experiments which quantify the impact of paddock management (summer weeds, stubble amount and configuration, grazing by livestock, cultivation) on the capture, storage and subsequent use of summer fallow rain.

The potential value of summer fallow rain as a resource to wheat production is generally significant across the region studied, but varies greatly according to soil type and rainfall pattern, amount and distribution. In the central west of NSW, where rainfall distribution is almost equi-seasonal, growing season rainfall is relatively low and soil plant available water capacity high, summer fallow rainfall potentially contributes 57% of mean simulated yield. In the northern wheat-belt of WA, where rainfall distribution is strongly Mediterranean, growing season rainfall reliable and soil plant available water capacity low, summer fallow rainfall contributes on average only 13% of mean simulated yield.

Field experiments being conducted at Temora, Condobolin and Hopetoun (Vic.) as part of GRDC's national water-use efficiency initiative are demonstrating that;

  1. Stubble does very little to reduce evaporation over summer at typical levels. It can significantly improve infiltration of summer rainfall events, particularly in locations subject to more intense rainfall events and on soil types susceptible to surface sealing (e.g. Temora). However, stubble can significantly reduce evaporation during autumn and winter.
  2. Summer weeds have by far the biggest and most reliable effect on summer fallow efficiency, and investment in control in most regions is low in risk and very profitable.
  3. The principal effect of livestock on fallow efficiency appears due to removal of cover rather than surface compaction resulting from trampling.
  4. Cultivation can increase or decrease fallow efficiency according to diverse site and season specific mechanisms. Its most reliable effect is through weed control.

Possible management changes, including novel genotypes which can make better use of stored soil water, will also be discussed.

Contact: James Hunt, Email: james.hunt@csiro.au

Phone: 02 6146 5066

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